Fluid-dispensing chip

ABSTRACT

A fluid-dispensing chip has a wafer substrate that incorporates drive circuitry. A nozzle assembly is positioned on the wafer substrate. The nozzle assembly has nozzle chamber walls and a roof wall that define a nozzle chamber and a fluid ejection port in the roof wall and an electrostatic actuator. The actuator has a first planar electrode positioned on the wafer substrate. A second planar electrode is positioned in the nozzle chamber and is displaceable towards and away from the first planar electrode to eject fluid from the fluid ejection port. The first planar electrode and the second planar electrode are connected to the drive circuitry so that a potential difference can be applied between the planar electrodes to displace the second planar electrode towards and away from the first planar electrode. At least one of the nozzle chamber walls and the wafer substrate define a fluid inlet in fluid communication with the nozzle chamber and a fluid supply source.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The following Australian provisional patent applications arehereby incorporated by cross-reference. For the purposes of location andidentification, US patent applications identified by their US patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the US patent applications claim the right ofpriority. US Patent Application Cross-Referenced (Claiming Right ofPriority Australian from Australian Provisional Patent No. ProvisionalApplication) Docket No. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02PO7988 09/113,073 ARTO3 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO799O 09/113,059 ART46PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60PO9399 09/112,791 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66PPO959 09/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO807209/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO804709/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO806309/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO806909/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO804809/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO800109/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO800209/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO803409/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO800409/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO804209/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO939109/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP089009/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP089009/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP259309/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP398509/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO793609/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO805409/112,828 IJM05 PO8065 09/113,111 IJM06 PO8055 09/113,108 IJM07 PO805309/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO795009/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO805909/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO807509/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO805209/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO807409/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO805809/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 09/113,089 IJM28 PO795209/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO939209/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP088209/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP398909/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP398609/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP089509/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP088709/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP088609/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP087709/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP088309/112,775 IR19 PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO800609/113,100 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04PO8010 09/113,064 MEMS05 PO8011 09/113,082 MEMS06 PO7947 09/113,081MEMS07 PO7944 09/113,080 MEMS09 PO7946 09/113,079 MEMS10 PO939309/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

FIELD OF THE INVENTION

[0003] The present invention relates to fluid dispensing. In particular,this invention discloses a fluid-dispensing chip.

BACKGROUND OF THE INVENTION

[0004] This invention is a development of a printing technology that hasbeen developed by the Applicant. This development can be traced byconsidering the referenced patents/patent applications set out above.

[0005] Many different types of printing have been invented, a largenumber of which are presently in use. The known forms of printing have avariety of methods for marking the print media with a relevant markingmedia. Commonly used forms of printing include offset printing, laserprinting and copying devices, dot matrix type impact printers, thermalpaper printers, film recorders, thermal wax printers, dye sublimationprinters and ink jet printers both of the drop on demand and continuousflow type. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

[0006] In recent years, the field of ink jet printing, wherein eachindividual pixel of ink is derived from one or more ink nozzles hasbecome increasingly popular primarily due to its inexpensive andversatile nature.

[0007] Many different techniques of ink jet printing have been invented.For a survey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

[0008] Ink Jet printers themselves come in many different types. Theutilisation of a continuous stream of ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1941001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

[0009] U.S. Pat. 3596275 by Sweet also discloses a process of continuousink jet printing including the step wherein the ink jet stream ismodulated by a high frequency electro-static field so as to cause dropseparation. This technique is still utilized by several manufacturersincluding Elmjet and Scitex (see also U.S. Pat. No. 3373437 by Sweet etal)

[0010] Piezoelectric ink jet printers are also one form of commonlyutilized ink jet printing device. Piezoelectric systems are disclosed byKyser et al. in U.S. Pat. No. 3946398 (1970) which utilises a diaphragmmode of operation, by Zolten in U.S. Pat. 3683212 (1970) which disclosesa squeeze mode of operation of a piezoelectric crystal, Stemme in U.S.Pat. No. 3747120 (1972) discloses a bend mode of piezo-electricoperation, Howkins in U.S. Pat. No. 4459601 discloses a Piezoelectricpush mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No.4584590 which discloses a sheer mode type of piezoelectric transducerelement.

[0011] Recently, thermal ink jet printing has become an extremelypopular form of ink jet printing. The ink jet printing techniquesinclude those disclosed by Endo et al in GB 2007162 (1979) and Vaught etal in U.S. Pat. No. 4490728. Both the aforementioned referencesdisclosed ink jet printing techniques rely upon the activation of anelectrothermal actuator which results in the creation of a bubble in aconstricted space, such as a nozzle, which thereby causes the ejectionof ink from an aperture connected to the confined space onto a relevantprint media. Manufacturers such as Canon and Hewlett Packard manufactureprinting devices utilising the electro-thermal actuator.

[0012] As can be seen in the above referenced matters, Applicant hasdeveloped an ink jet printing technology that usesmicro-electromechanical components to achieve the ejection of ink. Theuse of micro-electromechanical components allows printhead chips to havea large number of densely packed nozzle arrangements without theproblems associated with heat build-up.

[0013] Applicant envisages that this technology can be used to dispensefluid. This invention is therefore intended to be a simple developmentof the technology that has already been the subject of many patentapplications filed by the Applicant.

SUMMARY OF THE INVENTION

[0014] According to the invention, there is provided a fluid-dispensingchip that comprises

[0015] a wafer substrate that incorporates drive circuitry, and

[0016] a nozzle assembly positioned on the wafer substrate, the nozzleassembly comprising

[0017] nozzle chamber walls and a roof wall that define a nozzle chamberand a fluid ejection port in the roof wall, and

[0018] an electrostatic actuator that comprises

[0019] a first planar electrode positioned on the wafer substrate, and

[0020] a second planar electrode that is positioned in the nozzlechamber and is displaceable towards and away from the first planarelectrode to eject fluid from the fluid ejection port, the first planarelectrode and the second planar electrode being connected to the drivecircuitry so that a potential difference can be applied between theplanar electrodes to displace the second planar electrode towards andaway from the first planar electrode,

[0021] at least one of the nozzle chamber walls and the wafer substratedefining a fluid inlet in fluid communication with the nozzle chamberand a fluid supply source.

[0022] Said first planar electrode and said second planar electrode maydefine an air gap between the first and second planar electrodes. Atleast one of the nozzle chamber walls and the substrate may define anair path in fluid communication with an external atmosphere so that airflows into and out of the air gap when the second planar electrode isdisplaced towards and away from the first planar electrode.

[0023] The electrodes may have facing surfaces that are coated with amaterial having a low coefficient of friction to reduce possibilities ofstiction. Said material may comprise substantiallypolytetrafluoroethylene.

[0024] Instead, or in addition, one of the first and second planarelectrodes may have at least one projection that extends towards theother electrode to ensure that the electrodes do not touch when thesecond planar electrode is displaced towards the first planar electrode.

[0025] Said second planar electrode may include a layer of stiffeningmaterial for maintaining a stiffness of the second planar electrode. Thestiffening material may be silicon nitride.

[0026] The roof wall may define a plurality of etchant holes tofacilitate etching of sacrificial layers during construction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Notwithstanding any other forms which may fall within the scopeof the present invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings, in which:

[0028]FIG. 1 is a sectioned side view of one embodiment of afluid-dispensing chip of the invention, in an operative condition.

[0029]FIG. 2 is a sectioned side view of the fluid-dispensing chip ofFIG. 1 in a quiescent condition.

[0030]FIG. 3 is a perspective cross-sectional view of another embodimentof the fluid-dispensing chip of the invention.

[0031]FIG. 4 is a close-up perspective cross-sectional view (portion Aof FIG. 3), of the fluid-dispensing chip of FIG. 3.

[0032]FIG. 5 is an exploded perspective view illustrating theconstruction of the fluid-dispensing chip of FIG. 3.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

[0033] In FIGS. 1 and 2, reference numeral 10 generally indicates asectioned side view of one embodiment of a fluid-dispensing chip of theinvention.

[0034] The fluid-dispensing chip may include a silicon wafer substrate12. A drive circuitry layer 14 is positioned on the wafer substrate 12.The drive circuitry layer 14 is in the form of a CMOS two-level metallayer that includes the drive and control circuitry for thefluid-dispensing chip 10.

[0035] A passivation layer 16 of silicon nitride is positioned on thedrive circuitry layer 14 to protect the drive circuitry layer 14. Afirst planar electrode 18 is embedded in the layer 16. The first planarelectrode 18 is of aluminum and is connected to the drive circuitrylayer 14.

[0036] The fluid-dispensing chip 10 includes a nozzle chamber wall 19and a roof wall 20 that define a nozzle chamber 22. The roof wall 20defines a fluid ejection port 44. A fluid-ejecting member 28 ispositioned in the nozzle chamber 22. The fluid-ejecting member 28 isplanar and is aligned with and parallel to the first planar electrode18.

[0037] The fluid-ejecting member 28 is positioned on a support formation34 that extends from the passivation layer 16. The support formation 34is dimensioned so that the fluid-ejecting member 28 is spaced a suitabledistance from the first electrode 18. The support formation 34 isconfigured so that an air gap 40 is encapsulated between thefluid-ejecting member 28 and the first electrode 18.

[0038] The fluid-ejecting member 28 includes a second planar electrode24 that is positioned in the nozzle chamber 22. The second planarelectrode 24 is also of aluminum and is also connected to the drivecircuitry layer 14. The drive circuitry layer 14 is connected to each ofthe electrodes 18, 24 so that a potential can be set up between theelectrodes 18, 24 so that they are attracted to one another. A layer 26of silicon nitride is positioned on the electrode 24 to impart aresilient flexibility to the fluid-ejecting member 28. Thus, when apotential is set up between the electrodes 18, 24, the fluid-ejectingmember 28 is deflected towards the first electrode 18, as shown inFIG. 1. When the potential is removed, the first electrode 18 returns toa quiescent position as shown in FIG. 2.

[0039] A layer 32 of polytetrafluoroethylene (PTFE) is positioned on thefirst electrode 18. A layer 36 of PTFE is positioned on the secondelectrode 24, intermediate the electrodes 18, 24. This ensures that theelectrodes 18, 24 do not stick to one another when the fluid-ejectingmember 28 is deflected towards the first electrode 18. In order furtherto prevent stiction between the electrodes 18, 24, a projection 38 ispositioned on the fluid-ejecting member 28. The projection 38 bearsagainst the layer 32 to ensure that there is no contact between thelayers 32, 36.

[0040] The nozzle chamber wall 19 defines fluid inlet openings 30 thatare in fluid communication with a fluid supply so that the nozzlechamber 22 can be supplied with fluid. Fluid flows into a space 41defined by the roof wall 20, the nozzle chamber wall 19, thefluid-ejecting member 28 and the support formation 34. It will beappreciated that this occurs when the fluid-ejecting member 28 is drawntowards the first electrode 18. When the potential is reversed, thefluid-ejecting member 28 is urged away from the first electrode 18 sothat a drop 42 of fluid is ejected from the fluid ejection port 44. Thefluid-ejecting member 28 could have sufficient resilience so that areversal of potential is not necessary. In this case, release of elasticenergy as the fluid-ejecting member 28 returns to its quiescentcondition ensures the ejection of the fluid drop 42.

[0041] The roof wall 20 defines a rim 46 about the fluid ejection port44.

[0042] In FIGS. 3 to 5, reference numeral 50 generally indicates anotherembodiment of a fluid-dispensing chip of the invention. With referenceto FIGS. 1 and 2, like reference numerals refer to like parts, unlessotherwise specified.

[0043] The fluid-ejecting member 28 has a peripheral portion 52 that ispositioned between the nozzle chamber wall 19 and the layer 26 ofsilicon nitride. A corrugated annular portion 54 is positioned adjacentto the peripheral portion 52. A fluid-ejecting portion 56 defines aremainder of the fluid-ejecting member 28.

[0044] The electrodes 18, 24 and their respective PTFE layers 32, 36 aredimensioned to define the air gap 40.

[0045] The corrugated portion 54 is configured to expand when the secondelectrode 24 is displaced towards the first electrode 18. The siliconnitride layer 26 imparts a resilient flexibility to the corrugatedportion 54. Thus, the second electrode 24 returns to a quiescentcondition when the electrical potential is removed.

[0046] The nozzle chamber wall 19 is shaped to define four radiallyspaced fluid inlet supply channels 58 that are in fluid communicationwith the space 41. These allow fluid to flow into the space 41 when thesecond electrode 24 is drawn towards the first electrode 18.

[0047] The nozzle chamber wall 19 defines air spaces 60 that are influid communication with the air gap 40. These allow the passage of airwhen the second electrode 24 moves towards and away from the firstelectrode 18.

[0048] The roof wall 20 has a plurality of etchant openings 62 definedtherein to facilitate the etching of sacrificial material used in thefabrication of the chip 50. The etchant openings 62 are small enough toinhibit the passage of fluid as a result of surface tension effects.

[0049] It is important to note that the fluid-dispensing chip 10, 50 isessentially a micro-electromechanical systems (MEMS) device. A methodfor fabricating the device can readily be deduced from the descriptionin referenced application no: U.S. Pat. No. 09/112,787 and in many ofthe other referenced applications.

[0050] Applicant envisages that the fluid-dispensing chip 10, 50 will beparticularly suited for lab-on-a-chip applications. It can also beapplied to DNA/RNA arrays, protein chips and sensing and dosing. Thefluid-dispensing chip 10, 50 could also be used for drug deliverysystems.

[0051] Numerous variations and/or modifications may be made to thepresent invention as shown in the preferred embodiment without departingfrom the spirit or scope of the invention as broadly described. Thepreferred embodiment is, therefore, to be considered in all respects tobe illustrative and not restrictive.

1. A fluid-dispensing chip that comprises a wafer substrate thatincorporates drive circuitry, and a nozzle assembly positioned on thewafer substrate, the nozzle assembly comprising nozzle chamber walls anda roof wall that define a nozzle chamber and a fluid ejection port inthe roof wall, and an electrostatic actuator that comprises a firstplanar electrode positioned on the wafer substrate, and a second planarelectrode that is positioned in the nozzle chamber and is displaceabletowards and away from the first planar electrode to eject fluid from thefluid ejection port, the first planar electrode and the second planarelectrode being connected to the drive circuitry so that a potentialdifference can be applied between the planar electrodes to displace thesecond planar electrode towards and away from the first planarelectrode, at least one of the nozzle chamber walls and the wafersubstrate defining a fluid inlet in fluid communication with the nozzlechamber and a fluid supply source.
 2. A fluid-dispensing chip as claimedin claim 1, wherein said first planar electrode and said second planarelectrode define an air gap between the first and second planarelectrodes.
 3. A fluid-dispensing chip as claimed in claim 2, in whichat least one of the nozzle chamber walls and the substrate define an airpath in fluid communication with an external atmosphere so that airflows into and out of the air gap when the second planar electrode isdisplaced towards and away from the first planar electrode.
 4. Afluid-dispensing chip as claimed in claim 1, wherein the electrodes havefacing surfaces that are coated with a material having a low coefficientof friction so as to reduce possibilities of stiction.
 5. Afluid-dispensing chip as claimed in claim 4, wherein said materialcomprises substantially polytetrafluoroethylene.
 6. A fluid-dispensingchip as claimed in claim 1, in which one of the first and second planarelectrodes has at least one projection that extends towards the otherelectrode to ensure that the electrodes do not touch when the secondplanar electrode is displaced towards the first planar electrode.
 7. Afluid-dispensing chip as claimed in claim 1, wherein said second planarelectrode includes a layer of stiffening material for maintaining astiffness of said second planar electrode.
 8. A fluid-dispensing chip asclaimed in claim 7, wherein said stiffening material is silicon nitride.9. A fluid-dispensing chip as claimed in claim 1, wherein the roof walldefines a plurality of etchant holes to facilitate etching ofsacrificial layers during construction.